Cleaning of rails

ABSTRACT

In apparatus for the treatment of rails, for the purpose of improving wheel-rail adhesion, using a plasma torch or torches supported on a vehicle, means is provided for continuously guiding the torch or torches so that it or they is or are directed along the rail center line or a line parallel thereto. For this purpose, use may be made of an electromagnetic detector mounted on a carrier for the plasma torch or torches and adapted for transmitting an error signal, proportional to lateral displacement in relation to the rail cent center line, to servo mechanism operative on the said carrier for reducing the said displacement.

United States Patent Ogilvy et al.

1151 3,685,454 [451 Aug. 22, 1972 i541 CLEANING OF RAILS Inventors: Harry Reggie Ogilvy; Elizabeth Margaret Tuck; David John Miller Dobbs; John Anthony Roser, all of London, England Assignee: British Railways Board, London,

England Filed: Aug. 17, 1970 Appl. No.: 64,345

Foreign Application Priority Data Aug. 22, 1969 Great Britain ..42,036/69 US. Cl ..l04/l R, 104/279, 2l9/l2l P,

246/428 Int. Cl. ..B23k 9/00 Field of Search ..2l9/l2l P; 104/8, 1 R, 279; 73/678 S; 240/428 [561 1 rmfiilw i WM UNITEDSTATES PA'IENTS 2,111,872 3/1938 Rea ..2l9ll2lP 3,028,751 4/1962 Joy...........................73/67.85

Primary Examiner-Arthur L. La Point Assistant Examiner-George H. Libman Attorney-Sommers & Young ABSTRACT In apparatus for the treatment of rails, for the purpose of improving wheel-rail adhesion, using a plasma torch or torches supported on a vehicle, means is provided for continuously guiding the torch or torches so that it or they is or are directed along the rail center line or a line parallel thereto. For this purpose, use may be made of an electromagnetic detector mounted on a carrier for the plasma torch or torches and adapted for transmitting an error signal, proportional to lateral displacement in relation to the rail cent center line, to servo mechanism operative on the said carrier for reducing the said displacement.

4 Claims, 5 [having Figures PATENTEDauszz 1912 SHEET 1 BF 3 FIG. I

W Jowmtw-nw PATENTED 1922 I97? 3 685 454 sum 2 BF 3 HARRY H. 0mm ELIZABETH M.TucK DAVID .m. DOBBS JOHN A. R0$SER PATENTEDA B I 3.685.454

SHEET 3 OF 3 FIG 5 Ila HARRY H. OGILVY ELIZABETH P K DAVID J.M. D0585 JOHN A. ROSSER bYJW% CLEANING or RAILS This invention concerns improvements relating to the treatment of rails, for the purpose of improving wheel-rail adhesion of railway locomotive and other vehicles, by the use of arc-plasma techniques.

As the gauge of a railway line is held to close limits, it might appear that plasma torches mounted on a vehicle over the rail head, would, by moving with the vehicle, stay at all times in a desired position above the rail. Due, however, to wheel conicity and rail cant, a vehicle in motion will move from side to side in relation to the gauge width. This movement, coupled with end play in axle bearings and oscillation of sprung masses, permits considerable lateral movement relative to the rail of any equipment, such as a plasma torch, mounted on the vehicle. To achieve effective rail treatment, however, a plasma jet must be positioned to act upon the head of the rail. A large amplitude of oscillation reduces the effective time of contact between the jet and rail head.

To ensure that the rail is treated by the plasma jet at all times, a large number of torches can be mounted in a line transverse to the rail so that, despite oscillation, one or more of the torches always acts upon the rail head. Since each torch may be working with a power of kW or more and eight or more torches might be required to cover the range of oscillatory movement, the wastage of electrical power and of gas would render the system economically unattractive. The present invention seeks to provide an arrangement by which effective action upon the rail head can be ensured at all times, using a minimum number of torches.

According to the invention, therefore, it is proposed that a torch or torches supported on a vehicle should be continuously guided with respect to the center of the rail head in such a manner that the plasma jet or jets is or are directed along the rail center line or a line parallel thereto. The number of plasma torches required can then be reduced, treatment being confined substantially to the head of the rail. Advantageously, for this purpose, a detector mounted on a carrier for the plasma torch or torches is adapted for transmitting an error signal, proportional to lateral displacement in relation to the rail center line, to servo mechanism operative on the said carrier for reducing the said displacement.

Preferably the detector is electromagnetic, in which case it may comprise an E-shaped core disposed with the limbs directed vertically downwards with the center limb normally above the rail center line, balanced primary windings excited with alternating current being provided on the outer limbs and a secondary signalproducing winding on the middle limb.

With such apparatus, using a detector which is no closer than the plasma torch to the rail head, an adequate error signal can be obtained which, for small horizontal displacements, is approximately proportional to the displacement and can be differentiated with respect to the direction of displacement. Although the error signals produced may not be independent of the distance of the detector above the rail head, difficulty from this cause is avoided, as the balance position for zero displacement remains unaffected.

To minimize the effect of lateral movement, plasma torches should be mounted as nearly as possible to a wheel set of the vehicle, as the wheel sets are the only parts in contact with the rail. Mounting of torches on a bogie frame or the main chassis would introduce mechanical oscillations related to the springing. For minimal movement, the torches should therefore be mounted on a beam or other member fixed to the axlebox ends.

One manner in which the invention can be carried into effect will now be more fully described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic plan view of torch and detector suspension means,

FIG. 2 a side view thereof, also showing a bogie,

FIG. 3 a view to a larger scale illustrating the position of the detector in relation to the rail.

FIG. 4 a voltage/displacement diagram, and

FIG. 5 a block diagram for the control circuit.

In this example, for each rail 1 (FIGS. 1 and 2), a group of plasma torches 2 is to be maintained in a substantially constant position, transversely in relation to the rail head, regardless of lateral motion of a bogie frame 3 (FIG. 2) from which the torches are supported. The torches are suspended from a carrier framework comprising longitudinal beams 4 mounted on the axle boxes 5 of the bogie, so that the guidance system to be described has to compensate only for relative movement between axle-boxes and rail and not for that between bogie frame and rail. For each rail, the torches 2 are mounted on a transversely swingable carrier 6 which is pivotally suspended at 7 from brackets on the beam 4 and is pivotally coupled at 7a to the rod 8 of a hydraulic actuator 9 whose cylinder is fixed to a cross member 10 of the carrier frame. A detector head 11 to be described is also mounted on the carrier 6. FIG. 1 shows the above-described arrangement for one rail 1 only. It would be duplicated for the other rail.

The detector head 11 employed in this example to determine the torch position relative to the center of the rail head and to produce an error signal proportional to the relative transverse displacement is of a differential electromagnetic nature. As shown in FIG. 3, the head 11 comprises an E-shaped iron core 12 supported above the rail 1 at right angles thereto with the limbs of the E directed vertically downwardly. The outer limbs of the core carry similar primary, exciting, windings l3 supplied with alternating current and the middle limb a secondary, search," winding 14. With the core 12 symmetrically above the center line of the rail head (as shown), there will be substantially no flux linked with the winding 14 and no voltage will be induced therein, subject naturally to manufacturing tolerances and magnetic or mechanical asymmetry of the rail head. If the core 12 becomes displaced in relation to the rail head, the asymmetry will cause a flux to be produced in the middle limb and a voltage to be induced in the search winding 14. This voltage is then available as displacement error signal, the signal being zero for zero displacement.

By way of example, the detector head may suitably have the following characteristics: The exciting windings l3 consist each of turns of No. 36 standard wire gauge enameled wire, their resistance in series being 1 L5 ohms and their impedance, at a frequency of 775 Hz, 40.8 ohms. The search winding 14 consists of 300 turns of similar wire. These windings can be accommodated on a compact core (overall cross-sectional dimensions 3.6 by 1.25 inches) composed of 40 laminations, 0.02 inches thick. Because of the difficulty of winding the coils l3 identically, the position of one coil may be adjusted slightly, after winding, until substantially zero output is obtained from the winding 14 in a symmetrical position of the detector head, the core 11 being then potted in a hardening material to fix the positions of the windings. To permit of final balancing, preferably with the detector head in the position it will occupy in service, one winding 14 may be shunted by an adjustable high-value resistor.

FIG. 4 illustrates the nature of the response that can be obtained with such a detector head. This output voltage V from the search winding 14 is shown plotted against displacement d, in inches, of the head 11 on either side of the position of symmetry. The curves a, b, and c show the response obtained with the detector head positioned 1.75, 2.25, and 2.75 inches respectively above the head of the rail 1, the excitation voltage supplied to the windings 13 being 8 volts (peak to peak). The gain of the detector head, expressed in volts per unit of displacement, is substantially inversely proportional to the distance above the rail. By operating the system from a set zero-displacement position, variations in the said distance will affect the gain but not the balance position.

For displacements exceeding about i 1.5 to 2 inches, the output voltage falls off. Means, for example mechanical stops, should be provided to prevent the detector head from attaining these displacements, as otherwise the system would be liable to lock out at one end of its travel after passing over points, crossings or other material divergences for normal rail alignment.

A suitable system for the control of the hydraulic actuator 9 in dependence upon the output signal from the search winding 14 of the detector head 11 is illustrated diagrammatically in FIG. 5. Alternating current is supplied to the exciting windings 13 from a source comprising an oscillator 15 and power amplifier 16. As indicated at 1 la, this source may serve also a similar control system, with its own detector voltage of the winding 14 is supplied through a 50 Hz filter 17 to an A.C. amplifier 18.

In the example discussed above, a frequency of 775 Hz was referred to. For simplicitys sake, the detector head could be excited at 50 Hz, but this would be subject to disturbance from other 50-cycle supplies, notably for traction purposes where rail currents of 1,000 amperes may be encountered. Because of the risk of disturbance by harmonics, multiples of 50 Hz should also be avoided. Frequencies used in railway signal circuits are also to be excluded. Conveniently, therefore, an appreciably higher frequency (say i the range up to 1,000 Hz) satisfying these requirements is employed, a filter being incorporated to prevent 50 Hz interference.

The filtered output is passed to a phase-sensitive demodulator 19 to which a reference voltage from the amplifier 16 is also supplied through a transformer 20. The voltage output of the demodulator 19 is fed by way of amplifying means 21, which may include a dif- 6 ferential amplifier followed by a servo amplifier, to an electromagnetic valve 22, the signal at this point being a DC. current representative, by its magnitude an direction, of the magnitude and direction of the displacement of the detector head 11. The valve 22 controls the supply of hydraulic fluid under pressure to, and its exhaust from, the ends of the actuator 9, thereby producing correctional displacement of the detector head 11 and of the torches 2 until the said head again occupies a symmetrical position in relation to the rail head and there is no longer any displacement error signal from the search winding 14. A velocity feedback loop 23 is provided between the actuator 9 and the amplifier 18. Such a control system, illustrated in sim plified form only, has a high speed of response and is stable in operation.

It is unnecessary to describe the electrical components of the system in detail as these can be of known conventional electronic design using transistors or other solid-state devices. The electromagnetic valve and hydraulic actuator may likewise be of known conventional design. The electronic elements may conveniently be disposed in a casing housing the detector head 11 in a separate end compartment.

The torches employed may also be of known type, but are preferably operated in the non-transferred mode. The number of torches to be provided will depend upon the requirements of the case. The abovedescribed arrangement, provided with two torches, or even one torch, per rail will be very effective for improving wheel-rail adhesion for the vehicle on which the plasmatorch equipment is mounted. However, vehicles without such equipment subsequently passing over the rail may not obtain the same benefit from the previous passage of an equipped vehicle because their wheel-rail contact zones may not be the same. Provision may therefore be made of sufficient torches to cover the required width or the whole width of the rail head. Not more than four torches will normally be needed for this purpose. if more than one torch is provided on a carrier 6, the torches may be disposed side by side or in a staggered arrangement, as indicated in FIG. 1.

Other forms of position detector may be employed, for example an electrostatic detector or an optical detector using a reflected beam of light. Also means other than a hydraulic actuator may be used for displacing the torch an detector carrier. Thus the carrier may be mounted in linear bearings on the frame carried by the axle boxes and may be traversed by a threaded rod driven by a servo-motor whose split field is fed from the phase-sensitive demodulator l9, feed back being from a tachometer generator driven by the motor. As an alternative for the winding arrangement described a single primary winding may be arranged on the middle limb of the core 12 and two secondary windings on the other limbs or the adjacent halves of the shank. In this case, the difference between the voltages induced in the latter windings on relative displacement of the detector head provides the displacement error signal.

We claim:

1. Apparatus for the treatment of a rail for the purpose of improving wheel-rail adhesion, comprising:

at least one plasma torch,

a carrier supporting the said torch, from the vehicle,

over the said rail,

an electromagnetic detector mounted on the said carrier and adapted for transmitting an error signal middle limb.

3. Apparatus according to claim 1, wherein a phasesensitive device which differentiates the error signals with respect to direction of displacement is included in the signal-transmitting circuit between the said detector and servo-mechanism.

4. Apparatus according to claim 1, wherein the said carrier for the plasma torch for treating a rail comprises a member fixed to the axle boxes of wheels running on that rail, of a wheel set of the vehicle. 

1. Apparatus for the treatment of a rail for the purpose of improving wheel-rail adhesion, comprising: at least one plasma torch, a carrier supporting the said torch, from the vehicle, over the said rail, an electromagnetic detector mounted on the said carrier and adapted for transmitting an error signal proportional to lateral displacement in relation to the rail center line, and servo mechanism to which the said signal is transmitted and which is operative on the said carrier for reducing the said displacement.
 2. Apparatus according to claim 1, wherein the said detector has an E-shaped core disposed with the limbs directed vertically downward with the center limb normally above the rail center line, balanced primary windings excited with alternating current on the outer limbs and a secondary signal-producing winding on the middle limb.
 3. Apparatus according to claim 1, wherein a phase-sensitive device which differentiates the error signals with respect to direction of displacement is included in the signal-transmitting circuit between the said detector and servo-mechanism.
 4. Apparatus according to claim 1, wherein the said carrier for the plasma torch for treating a rail comprises a member fixed to the axle boxes of wheels running on that rail, of a wheel set of the vehicle. 